Compressed air processing systems are known from German Patent No. DE 195 44 621 C1 corresponding to European Patent No. EP 0 776 807 B1, German Patent No. DE 196 38 226 C1 corresponding to European Patent No. EP 0 831 383 B1 and from German Patent No. DE 198 34 705 C2. These known compressed air processing systems include a common structural unit being formed by the pressure control unit, the air dryer and a multi-circuit protection valve. The multi-circuit protection valve for each circuit includes an overflow valve having limited backflow. Conduits lead from the overflow valve to the respective circuits. Usually, the containers of the circuits I and II are associated with the two circuits of an overall brake system. Additional circuits serve to supply the hand brake valve and secondary aggregates. In this way, there may also be a fifth circuit including an overflow valve of the multi-circuit protection valve and leading to a reservoir container via a conduit. The reservoir container is connected to the air suspension system of the motor vehicle. In this way, an air suspension system is supplied with compressed air. The known compressed air processing systems also include an electronic control unit, meaning a special control unit being coordinated with the compressed air processing system with which the respective valves of the pressure control unit, the air dryer and the multi-circuit protection valve are controlled.
An air suspension system for motor vehicles is known from German Patent Application No. DE 101 25 204 A1. The system is especially adapted to motor vehicles including air suspension. The system includes a level control unit for the respective suspension elements being located close to the wheels of the motor vehicle. The level control unit is supplied with electric potential by a battery, and it is connected to an electric CAN bus line such that the level control unit receives and processes electric signals. A common control line leads to the wheels and to the suspension elements, respectively, of an axle and thus to the right side and the left side of the motor vehicle. German Patent Application No. DE 101 25 204 A1 does not disclose whether the line is an electric line or a pneumatic control line. Furthermore, there is no disclosure concerning a compressed air processing system.
A method of filling an air suspension system by an air dryer is known from German Patent Application No. DE 100 38 266 A1. A compressor and an air dryer being located downstream of the compressor serve to supply and control the air suspension system. Downstream of a check valve being bypassed by a throttle, supply lines lead to controllable way valves being associated with the respective air suspension bellow. The pressure control unit further includes an exit valve. The pressure control unit may also be operated to serve for regeneration of the air dryer. An electronic control unit is associated with the air suspension system. The electronic control unit exclusively controls the elements of the air suspension system and the associated compressed air processing system. German Patent Application No. DE 10 38 266 A1 does not disclose any features of a brake system.
It is also known that trucks include a pneumatic brake system and a pneumatic air suspension system. The air suspension system is supplied with compressed air by a circuit of the compressed air processing system. This circuit is arranged in addition to the brake circuits. The air suspension system includes a plurality of valves at least partly being designed as electrically controllable solenoid valves. A separate electronic control unit serves to control these solenoid valves of the air suspension system. The separate electronic control unit is arranged at a different place than the electronic control unit of the air suspension system. For example, the separate electronic control unit is located in the region of the drivers cabin. Respective electric lines lead from the separate control unit to the solenoid valves of the air suspension systems. The structural expenditure and the assembly expenditure for the two electronic control units are substantial. In addition, the number of connections for electric supply of the two electronic control units and the number of pneumatic conduits on the motor vehicle is comparatively great.
An electronic system for a motor vehicle is known from German Patent No. DE 41 11 023 C2 corresponding to U.S. Pat. No. 5,351,776. The system includes a separate special control apparatus being associated with the respective element of the motor vehicle. For example, there is a special control apparatus for the motor, a special control apparatus for the transmission and a special control apparatus for the brake. A central control apparatus is arranged upstream of these special control apparatuses. The central control apparatus and the special control apparatuses are connected by bus lines such that electronic signals may be transmitted.